1. Field of the Invention
The present invention relates to a system and method of controlling the automatic, robotic driving of an vehicle to simulate controlled operator performance of the vehicle and, more particularly, for controlling the operation of a vehicle in correlation with a dynamometer so that the response of the vehicle can be accurately maintained to match the desired profiles of operation being monitored.
2. Description of Related Art
It has become a common practice in both the vehicle industry and government regulatory agencies to use dynamometers and other electro-mechanical devices to simulate road load and vehicle inertia forces for testing vehicles in place. The vehicle dynamometers can act as measuring devices for determining the torque and/or horsepower output of a vehicle and further as a simulation device for simulating the inertia and road load forces to which a vehicle is normally subjected during the actual operation of the vehicle. As can be readily appreciated, not only can the torque and horsepower output of the vehicle be determined, frequently there is a correlation with the analysis of the engine emissions to determine potential pollution associated with the performance of the vehicle relative to government guidelines. Because of the tight controls that are being imposed by government regulatory agencies, it is extremely important that any simulated vehicle driven operation on a chassis dynamometer be carried out as accurately as possible to improve the precision of the desired measurements. The vehicle can be subjected to a predetermined dynamic road ability test and the response of the vehicle should attempt to accurately match the requirements of such testing procedures.
To remove the subjective characteristics of having a human operator respond to the various performance criteria demanded, efforts have been made to utilize an automatic driving robot which can be installed in the vehicle under test to operate the various operator controls on a precise basis to enable an objective testing procedure to be achieved.
The automatic driving robot can be physically installed in the vehicle and a plurality of actuators can be individually driven by various force exerting means, such as oil pressure, air pressure, a DC motor or the like, to carry out the operation of controlling the accelerator pedal, a brake pedal, a clutch pedal and a switching operation of the shift lever, where required.
In operation, a predetermined vehicle drive simulation procedure is utilized and it is necessary to drive the vehicle in accordance with this predetermined driving pattern. For example, in order to control a throttle servo system and/or alternatively the brake servo system, a difference between a nominal velocity VNOM and the actual velocity of the vehicle VACT on the chassis dynamometer must be controlled.
Reference can be made to FIG. 3 for a schematic example of such a conventional system wherein the roller surface velocity signal of the chassis dynamometer 1 is linked into a PI (proportional and integral) control system 2 to feed back control associated with the opening of a throttle servo system 3. Within the PI control system 2, a multiplier circuit 4 and an integrator circuit 5 can be utilized. These functions can also frequently be performed with a microprocessor system. In the schematic, reference number 6 designates an engine that is responsive to the throttle servo system 3, reference number 7 designates a power train as the power transmission system, and reference points 8 and 9 are designated as butt points (a.k.a. summing points), wherein the sum of two signals can be added or subtracted.
A problem which has occurred in the conventional system is that a significant delay occurs in both the operated and controlled quantity of the throttle and/or brake at a so-called change over speed point in the predetermined driving pattern. Thus, when an acceleration is suddenly changed, such as from an accelerated drive to a stationary driving mode of operation or from a stationary driving operation to a reduced speed drive operation and then, for example, from a reduced speed driving operation to again an accelerated driving operation, a significant disadvantage occurs in that an overshooting relative to the desired predetermined driving pattern frequently occurs and erroneous information can be introduced into the performance of the vehicle.
Thus, there is still a need in the art to provide an improved system for controlling an automatic driving of an vehicle for monitoring its performance in an economical manner in order to create an objective and repetitive testing system.